Which of the following statements are true? A. Frequency division multiplexing technique can be handled by digital circuits. B. Time division multiplexing technique can be handled by analog circuits C. Wavelength division multiplexing technique is used with optical fiber for combining two signals. D. Frequency division multiplexing technique can be applied when the bandwidth of a link is greater than the bandwidth of the signals to be transmitted. Choose the correct answer from the options given below :
C and D only
Understanding different multiplexing techniques like Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), and Wavelength Division Multiplexing (WDM) is crucial in data communication. Let's analyze each statement to determine its truthfulness.
Analyzing Multiplexing Statements
We will evaluate each statement about multiplexing techniques:
- Statement A: Frequency division multiplexing technique can be handled by digital circuits.
Frequency Division Multiplexing (FDM) is fundamentally an analog technique. It works by splitting the total bandwidth of a communication channel into multiple distinct frequency bands. Each frequency band is used to transmit a separate signal simultaneously. While digital signals can be modulated onto analog carriers and then multiplexed using FDM, the core multiplexing process itself, involving the separation and combining of signals based on frequency, is performed using analog filters and circuitry. Handling FDM primarily involves analog processes, not digital circuits directly manipulating the frequency bands in a digital manner.
Therefore, statement A is false.
- Statement B: Time division multiplexing technique can be handled by analog circuits.
Time Division Multiplexing (TDM) is primarily a digital technique. It works by dividing the communication channel's time into small time slots. Each user or signal is allocated specific time slots in a repeating cycle. Signals are transmitted in bursts during their allocated time slots. This technique relies heavily on digital sampling (for analog signals), timing, synchronization, and switching, which are all functions typically performed by digital circuits. While analog signals can be sampled and then multiplexed using TDM, the core TDM process is digital.
Therefore, statement B is false.
- Statement C: Wavelength division multiplexing technique is used with optical fiber for combining two signals.
Wavelength Division Multiplexing (WDM) is a multiplexing technique specifically used in optical fiber communication. It works by combining multiple optical signals, each transmitted at a different wavelength (which is analogous to frequency in light waves), onto a single optical fiber. Demultiplexing at the receiving end separates these signals based on their wavelengths. This allows for transmitting multiple data streams simultaneously over a single fiber, significantly increasing its capacity. WDM is indeed used for combining multiple signals (two or more) in optical fiber communication.
Therefore, statement C is true.
- Statement D: Frequency division multiplexing technique can be applied when the bandwidth of a link is greater than the bandwidth of the signals to be transmitted.
Frequency Division Multiplexing (FDM) requires that the total available bandwidth of the communication link be divided among the signals being transmitted. Each signal occupies a specific frequency band, and these bands must be separated by guard bands to prevent interference. For this to work, the total available bandwidth of the link must be sufficient to accommodate the bandwidth required by all the individual signals plus the necessary guard bands. Thus, the bandwidth of the link must be greater than or equal to the sum of the bandwidths of the signals being transmitted (plus guard bands). This statement correctly captures the necessary condition that the link's capacity (bandwidth) must exceed the requirements of the signals to be multiplexed using FDM.
Therefore, statement D is true.
Summary of Statements
Based on the analysis:
- Statement A: False
- Statement B: False
- Statement C: True
- Statement D: True
The true statements are C and D.
Conclusion
The statements that are true are C and D.
| Statement | Technique | Description Summary | Truth Value |
|---|---|---|---|
| A | FDM | Handled by digital circuits | False |
| B | TDM | Handled by analog circuits | False |
| C | WDM | Used with optical fiber for combining signals | True |
| D | FDM | Link bandwidth > signal bandwidths condition | True |
Revision Table: Data Multiplexing Techniques
| Technique | Method | Domain | Used For |
|---|---|---|---|
| Frequency Division Multiplexing (FDM) | Divides bandwidth into frequency channels. | Analog (can carry analog or modulated digital) | Radio broadcasting, TV, early telephony |
| Time Division Multiplexing (TDM) | Divides time into time slots. | Digital (can carry digital or sampled analog) | Digital telephony (e.g., T1/E1 lines), cellular networks |
| Wavelength Division Multiplexing (WDM) | Combines multiple light wavelengths onto one fiber. | Optical | Fiber optic communication systems |
Additional Information on Multiplexing
Multiplexing is a technique used to combine multiple data streams into a single stream to be transmitted over a shared medium. This allows efficient use of the communication channel capacity.
- Frequency Division Multiplexing (FDM): This is like having multiple radio stations broadcasting at different frequencies simultaneously over the airwaves. Each station uses a distinct frequency band, and your radio tuner selects the desired frequency to listen to a specific station.
- Time Division Multiplexing (TDM): Imagine several people sharing a single phone line, but instead of talking over each other, they take turns speaking for very short, fixed durations. The system quickly cycles through each person, giving them a slot of time to transmit their data.
- Wavelength Division Multiplexing (WDM): This is specific to fiber optics. Think of different colored lights traveling down a single glass fiber. Each color (wavelength) can carry a different signal. At the other end, optical filters separate the colors back into individual signals. Dense Wavelength Division Multiplexing (DWDM) is an advanced form that uses many more wavelengths.
Understanding when and how each multiplexing technique is used is important for studying data communication and networking.
Important Questions from Multiplexer
The device which changes from serial data to parallel data is:
Consider a logic gate circuit. with 8 input lines (D 0, D 1..... D 7) and 3 output lines (A 0, A 1, A 2) specified by following operations
A 2= D 4+ D 5+ D 6+ D 7
A 1= D 2+ D 3+ D 6+ D 7
A 0= D 1+ D 3+ D 5+ D 0
Where + indicates logical OR operation. This circuit is
Consider the sentence below.
There is a country that borders both India and Pakistan.
Which of the following logical expressions express the above sentence correctly when the predicate Country(x) represents that x is a country and Borders(x, y) represents that the countries x and y share the border?
A digital computer has a common bus system for 8 registers 16 bits each. How many multiplexers are required to implement common bus? What size of multiplexers is required?
In a multiplexer, the number of input lines is ‘n’ and the number of select lines is ‘m’. Which of the following is correct?
